Thirty years ago my girlfriend got pregnant. We decided to get an abortion.
The guy gets over it and moves on.
The woman does not.
I have numerous female friends who have had abortions. None of them regret it. But no matter how long ago it was, they all still "feel" it very much today. It is always present for them.
It's best to think of an abortion not like a medical procedure, but as a psychological one. Like therapy. It will change a person, and forever inform who they are, to themselves.
You are in a tough place, no doubt about it.
The only thing I can offer is this: The problem/issue/decision is over there, on the other side of the fence. You and Sarah are standing side by side looking over the fence at the problem/issue over there. Make sure you are ALWAYS in this stance... side by side together, addressing the problem. It is not HER problem. It is not YOUR problem.
And if it ever gets to "me vs you", break out of the moment, and role play. Switch roles. Argue the other person's side. This will help re-level the field, and get you both on the same page again.